This invention relates to catalytic reactor operation wherein a liquid phase is treated with a gaseous reactant. In particular it relates to a technique for contacting multi-phase reactants in a fixed porous catalyst bed under continuous countercurrent conditions, including methods and apparatus for controlling frothing in the reactor.
Chemical reactions between liquid and gaseous reactants present difficulties in obtaining intimate contact between phases. Such reactions are further complicated when the desired reaction is catalytic, and requires contact of both fluid phases with a solid catalyst. Numerous multi-phase reactor systems have been developed wherein a fixed porous bed of solid catalyst is retained in a reactor. Typically, fixed bed reactors have been arranged with the diverse phases being passed cocurrently over the catalyst, for instance as shown in U.S. Pat. Nos. 4,126,539 (Derr et al), 4,235,847 (Scott), 4,283,271 (Garwood et al), and 4,396,538 (Chen et al). In the petroleum refining industry, multi-phase catalytic reactor systems have been employed for dewaxing, hydrogenation, desulfurizing, hydrocracking, isomerization and other treatments of liquid feedstocks, especially distillates, lubricants, heavy oil fractions, residuum, etc,. Other known techniques for contacting liquid-gas mixtures with solid catalysts include slurry catalyst, ebullated bed and countercurrent systems, such as disclosed in U.S. Pat. Nos. 2,717,202, 3,186,935, 4,221,653, and 4,269,805. The above cited patents are incorporated herein by reference. While prior reactor systems are satisfactory for certain needs, efficient multi-phase contact has been difficult to achieve for many fixed bed applications.
It is an object of the present invention to provide a unique reactor system, including countercurrent operating techniques and apparatus for improved treatment of liquid with a gaseous reactant in a reactor containing a porous fixed bed of solid catalyst. It is a further object to provide such multi-phase reactor operating under controlled flow conditions to maintain a gas-liquid froth, while minimizing flow maldistribution patterns and providing optimum volumetric proportions of upwardly moving gas dispersed in a downwardly gravitating liquid phase.